1. Field of the Invention
The present invention relates in general to an ink-jet recording apparatus and a method of introducing ink accommodated in an ink package in the ink-jet recording apparatus. In particular, the present invention relates to such an apparatus capable of ejecting or delivering, with high stability, the ink accommodated in the ink package and a method of introducing the ink to the ink-jet recording apparatus with high stability, while reducing a cost required for packing or enclosing the ink package.
2. Discussion of Related Art
There is known an ink-jet recording apparatus which comprises an ink-jet printing head having nozzles through which ink is ejected to a recording medium, a mounting portion on which an ink package that accommodates the ink is removably mounted, and an ink-introducing device by which the ink accommodated in the ink package is introduced into the ink-jet printing head.
The ink used for the ink-jet recording apparatus is manufactured by a process including a step of dissolving an ink material in a solvent, and a step of filtering a solution of the ink material. Where the ink as manufactured by this process is accommodated in the ink package for use on the ink-jet recording apparatus, various kinds of gasses such as nitrogen, oxygen and carbon dioxide that are dissolved in the ink are introduced together with the ink into the ink-jet printing head, causing bubbles that may prevent the ink-jet printing head from smoothly ejecting droplets of the ink, giving rise to a risk of a poor ink-ejecting performance of the head. To avoid this drawback, it has been practiced to carry out a deaerating or degassing treatment of the ink, so as to reduce the amounts of the dissolved gases before the ink is accommodated in the ink package. This deaerating treatment involves an operation to stir the ink within a pressure vessel at a reduced pressure and an operation using a deaerating device equipped with a gas permeation membrane.
When the ink package in which the thus deaerated or degassed ink is accommodated is transported, or stored for a long time before its use, oxygen and other gases in the air may be dissolved in the ink. JP-B2-3-61592 (column 4, lines 4-7, and FIG. 1, in particular) discloses a technique to prevent the dissolution of such gases in the ink. According to this technique, an ink bag filled with the degassed ink is accommodated in a suitable ink-bag casing, and this ink-bag casing is placed in a vacuum chamber the pressure of which is adjusted to a reduced pressure lower than the atmospheric level, and is fluid-tightly enclosed or accommodated within a sealing wrapper or container such as a plastic or rubber bag or a metallic can or box, so that the casing is kept under the reduced pressure in the evacuated sealing wrapper, during transportation or storage.
To prevent a poor ink-ejecting performance of the ink-jet recording apparatus, the ink used for the apparatus is required to maintain a high degree or deaeration, as described above. Where all of the ink packages, including those for replacement, to be used on the ink-jet recording apparatus are packed or enclosed according to the above-indicated technique disclosed in JP-B2-3-61592, the cost required for packing or enclosing the ink package is inevitably increased, resulting in an increase in the running cost of the ink-jet recording apparatus.
The inventor of the present invention conducted experiments and found the following: The ink-ejecting performance of the ink-jet recording apparatus is largely influenced by the degree of deaeration of the ink in a case where the ink is initially introduced into the ink-jet printing head of the apparatus when the ink-jet printing head is initially used. As long as the ink having a relatively high degree of deaeration is introduced when the ink-jet printing head is initially used, the ink-ejecting performance of the apparatus is not largely influenced by the degree of deaeration of the ink even if the ink which is to be subsequently introduced into the ink-jet printing head has a degree of deaeration lower than that of the initially introduced ink.